Merge tag 'locking-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:

 - Micro-optimize local_xchg() and the rtmutex code on x86

 - Fix percpu-rwsem contention tracepoints

 - Simplify debugging Kconfig dependencies

 - Update/clarify the documentation of atomic primitives

 - Misc cleanups

* tag 'locking-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/rtmutex: Use try_cmpxchg_relaxed() in mark_rt_mutex_waiters()
  locking/x86: Implement local_xchg() using CMPXCHG without the LOCK prefix
  locking/percpu-rwsem: Trigger contention tracepoints only if contended
  locking/rwsem: Make DEBUG_RWSEMS and PREEMPT_RT mutually exclusive
  locking/rwsem: Clarify that RWSEM_READER_OWNED is just a hint
  locking/mutex: Simplify <linux/mutex.h>
  locking/qspinlock: Fix 'wait_early' set but not used warning
  locking/atomic: scripts: Clarify ordering of conditional atomics

arch/x86/include/asm/local.h

@@ -131,8 +131,20 @@ static inline bool local_try_cmpxchg(local_t *l, long *old, long new)
 				 (typeof(l->a.counter) *) old, new);
 }
 
-/* Always has a lock prefix */
-#define local_xchg(l, n) (xchg(&((l)->a.counter), (n)))
+/*
+ * Implement local_xchg using CMPXCHG instruction without the LOCK prefix.
+ * XCHG is expensive due to the implied LOCK prefix.  The processor
+ * cannot prefetch cachelines if XCHG is used.
+ */
+static __always_inline long
+local_xchg(local_t *l, long n)
+{
+	long c = local_read(l);
+
+	do { } while (!local_try_cmpxchg(l, &c, n));
+
+	return c;
+}
 
 /**
  * local_add_unless - add unless the number is already a given value

include/linux/atomic/atomic-arch-fallback.h

@@ -2005,6 +2005,7 @@ raw_atomic_xchg_relaxed(atomic_t *v, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_cmpxchg() elsewhere.
  *
@@ -2033,6 +2034,7 @@ raw_atomic_cmpxchg(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_cmpxchg_acquire() elsewhere.
  *
@@ -2061,6 +2063,7 @@ raw_atomic_cmpxchg_acquire(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_cmpxchg_release() elsewhere.
  *
@@ -2088,6 +2091,7 @@ raw_atomic_cmpxchg_release(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_cmpxchg_relaxed() elsewhere.
  *
@@ -2112,7 +2116,8 @@ raw_atomic_cmpxchg_relaxed(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_try_cmpxchg() elsewhere.
  *
@@ -2145,7 +2150,8 @@ raw_atomic_try_cmpxchg(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_try_cmpxchg_acquire() elsewhere.
  *
@@ -2178,7 +2184,8 @@ raw_atomic_try_cmpxchg_acquire(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_try_cmpxchg_release() elsewhere.
  *
@@ -2210,7 +2217,8 @@ raw_atomic_try_cmpxchg_release(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_try_cmpxchg_relaxed() elsewhere.
  *
@@ -2403,6 +2411,7 @@ raw_atomic_add_negative_relaxed(int i, atomic_t *v)
  * @u: int value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_fetch_add_unless() elsewhere.
  *
@@ -2432,6 +2441,7 @@ raw_atomic_fetch_add_unless(atomic_t *v, int a, int u)
  * @u: int value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_add_unless() elsewhere.
  *
@@ -2452,6 +2462,7 @@ raw_atomic_add_unless(atomic_t *v, int a, int u)
  * @v: pointer to atomic_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_inc_not_zero() elsewhere.
  *
@@ -2472,6 +2483,7 @@ raw_atomic_inc_not_zero(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_inc_unless_negative() elsewhere.
  *
@@ -2499,6 +2511,7 @@ raw_atomic_inc_unless_negative(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_dec_unless_positive() elsewhere.
  *
@@ -2526,6 +2539,7 @@ raw_atomic_dec_unless_positive(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_dec_if_positive() elsewhere.
  *
@@ -4117,6 +4131,7 @@ raw_atomic64_xchg_relaxed(atomic64_t *v, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_cmpxchg() elsewhere.
  *
@@ -4145,6 +4160,7 @@ raw_atomic64_cmpxchg(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_cmpxchg_acquire() elsewhere.
  *
@@ -4173,6 +4189,7 @@ raw_atomic64_cmpxchg_acquire(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_cmpxchg_release() elsewhere.
  *
@@ -4200,6 +4217,7 @@ raw_atomic64_cmpxchg_release(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_cmpxchg_relaxed() elsewhere.
  *
@@ -4224,7 +4242,8 @@ raw_atomic64_cmpxchg_relaxed(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_try_cmpxchg() elsewhere.
  *
@@ -4257,7 +4276,8 @@ raw_atomic64_try_cmpxchg(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_try_cmpxchg_acquire() elsewhere.
  *
@@ -4290,7 +4310,8 @@ raw_atomic64_try_cmpxchg_acquire(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_try_cmpxchg_release() elsewhere.
  *
@@ -4322,7 +4343,8 @@ raw_atomic64_try_cmpxchg_release(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_try_cmpxchg_relaxed() elsewhere.
  *
@@ -4515,6 +4537,7 @@ raw_atomic64_add_negative_relaxed(s64 i, atomic64_t *v)
  * @u: s64 value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_fetch_add_unless() elsewhere.
  *
@@ -4544,6 +4567,7 @@ raw_atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
  * @u: s64 value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_add_unless() elsewhere.
  *
@@ -4564,6 +4588,7 @@ raw_atomic64_add_unless(atomic64_t *v, s64 a, s64 u)
  * @v: pointer to atomic64_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_inc_not_zero() elsewhere.
  *
@@ -4584,6 +4609,7 @@ raw_atomic64_inc_not_zero(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_inc_unless_negative() elsewhere.
  *
@@ -4611,6 +4637,7 @@ raw_atomic64_inc_unless_negative(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_dec_unless_positive() elsewhere.
  *
@@ -4638,6 +4665,7 @@ raw_atomic64_dec_unless_positive(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic64_dec_if_positive() elsewhere.
  *
@@ -4662,4 +4690,4 @@ raw_atomic64_dec_if_positive(atomic64_t *v)
 }
 
 #endif /* _LINUX_ATOMIC_FALLBACK_H */
-// eec048affea735b8464f58e6d96992101f8f85f1
+// 14850c0b0db20c62fdc78ccd1d42b98b88d76331

include/linux/atomic/atomic-instrumented.h

@@ -1182,6 +1182,7 @@ atomic_xchg_relaxed(atomic_t *v, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_cmpxchg() there.
  *
@@ -1202,6 +1203,7 @@ atomic_cmpxchg(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_cmpxchg_acquire() there.
  *
@@ -1221,6 +1223,7 @@ atomic_cmpxchg_acquire(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_cmpxchg_release() there.
  *
@@ -1241,6 +1244,7 @@ atomic_cmpxchg_release(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_cmpxchg_relaxed() there.
  *
@@ -1260,7 +1264,8 @@ atomic_cmpxchg_relaxed(atomic_t *v, int old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_try_cmpxchg() there.
  *
@@ -1282,7 +1287,8 @@ atomic_try_cmpxchg(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_try_cmpxchg_acquire() there.
  *
@@ -1303,7 +1309,8 @@ atomic_try_cmpxchg_acquire(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_try_cmpxchg_release() there.
  *
@@ -1325,7 +1332,8 @@ atomic_try_cmpxchg_release(atomic_t *v, int *old, int new)
  * @new: int value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_try_cmpxchg_relaxed() there.
  *
@@ -1475,6 +1483,7 @@ atomic_add_negative_relaxed(int i, atomic_t *v)
  * @u: int value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_fetch_add_unless() there.
  *
@@ -1495,6 +1504,7 @@ atomic_fetch_add_unless(atomic_t *v, int a, int u)
  * @u: int value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_add_unless() there.
  *
@@ -1513,6 +1523,7 @@ atomic_add_unless(atomic_t *v, int a, int u)
  * @v: pointer to atomic_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_inc_not_zero() there.
  *
@@ -1531,6 +1542,7 @@ atomic_inc_not_zero(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_inc_unless_negative() there.
  *
@@ -1549,6 +1561,7 @@ atomic_inc_unless_negative(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_dec_unless_positive() there.
  *
@@ -1567,6 +1580,7 @@ atomic_dec_unless_positive(atomic_t *v)
  * @v: pointer to atomic_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_dec_if_positive() there.
  *
@@ -2746,6 +2760,7 @@ atomic64_xchg_relaxed(atomic64_t *v, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_cmpxchg() there.
  *
@@ -2766,6 +2781,7 @@ atomic64_cmpxchg(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_cmpxchg_acquire() there.
  *
@@ -2785,6 +2801,7 @@ atomic64_cmpxchg_acquire(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_cmpxchg_release() there.
  *
@@ -2805,6 +2822,7 @@ atomic64_cmpxchg_release(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_cmpxchg_relaxed() there.
  *
@@ -2824,7 +2842,8 @@ atomic64_cmpxchg_relaxed(atomic64_t *v, s64 old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_try_cmpxchg() there.
  *
@@ -2846,7 +2865,8 @@ atomic64_try_cmpxchg(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_try_cmpxchg_acquire() there.
  *
@@ -2867,7 +2887,8 @@ atomic64_try_cmpxchg_acquire(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_try_cmpxchg_release() there.
  *
@@ -2889,7 +2910,8 @@ atomic64_try_cmpxchg_release(atomic64_t *v, s64 *old, s64 new)
  * @new: s64 value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_try_cmpxchg_relaxed() there.
  *
@@ -3039,6 +3061,7 @@ atomic64_add_negative_relaxed(s64 i, atomic64_t *v)
  * @u: s64 value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_fetch_add_unless() there.
  *
@@ -3059,6 +3082,7 @@ atomic64_fetch_add_unless(atomic64_t *v, s64 a, s64 u)
  * @u: s64 value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_add_unless() there.
  *
@@ -3077,6 +3101,7 @@ atomic64_add_unless(atomic64_t *v, s64 a, s64 u)
  * @v: pointer to atomic64_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_inc_not_zero() there.
  *
@@ -3095,6 +3120,7 @@ atomic64_inc_not_zero(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_inc_unless_negative() there.
  *
@@ -3113,6 +3139,7 @@ atomic64_inc_unless_negative(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_dec_unless_positive() there.
  *
@@ -3131,6 +3158,7 @@ atomic64_dec_unless_positive(atomic64_t *v)
  * @v: pointer to atomic64_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic64_dec_if_positive() there.
  *
@@ -4310,6 +4338,7 @@ atomic_long_xchg_relaxed(atomic_long_t *v, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_cmpxchg() there.
  *
@@ -4330,6 +4359,7 @@ atomic_long_cmpxchg(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_cmpxchg_acquire() there.
  *
@@ -4349,6 +4379,7 @@ atomic_long_cmpxchg_acquire(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_cmpxchg_release() there.
  *
@@ -4369,6 +4400,7 @@ atomic_long_cmpxchg_release(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_cmpxchg_relaxed() there.
  *
@@ -4388,7 +4420,8 @@ atomic_long_cmpxchg_relaxed(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_try_cmpxchg() there.
  *
@@ -4410,7 +4443,8 @@ atomic_long_try_cmpxchg(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_try_cmpxchg_acquire() there.
  *
@@ -4431,7 +4465,8 @@ atomic_long_try_cmpxchg_acquire(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_try_cmpxchg_release() there.
  *
@@ -4453,7 +4488,8 @@ atomic_long_try_cmpxchg_release(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_try_cmpxchg_relaxed() there.
  *
@@ -4603,6 +4639,7 @@ atomic_long_add_negative_relaxed(long i, atomic_long_t *v)
  * @u: long value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_fetch_add_unless() there.
  *
@@ -4623,6 +4660,7 @@ atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
  * @u: long value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_add_unless() there.
  *
@@ -4641,6 +4679,7 @@ atomic_long_add_unless(atomic_long_t *v, long a, long u)
  * @v: pointer to atomic_long_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_inc_not_zero() there.
  *
@@ -4659,6 +4698,7 @@ atomic_long_inc_not_zero(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_inc_unless_negative() there.
  *
@@ -4677,6 +4717,7 @@ atomic_long_inc_unless_negative(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_dec_unless_positive() there.
  *
@@ -4695,6 +4736,7 @@ atomic_long_dec_unless_positive(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Unsafe to use in noinstr code; use raw_atomic_long_dec_if_positive() there.
  *
@@ -5008,4 +5050,4 @@ atomic_long_dec_if_positive(atomic_long_t *v)
 
 
 #endif /* _LINUX_ATOMIC_INSTRUMENTED_H */
-// 2cc4bc990fef44d3836ec108f11b610f3f438184
+// ce5b65e0f1f8a276268b667194581d24bed219d4

include/linux/atomic/atomic-long.h

@@ -1352,6 +1352,7 @@ raw_atomic_long_xchg_relaxed(atomic_long_t *v, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_cmpxchg() elsewhere.
  *
@@ -1374,6 +1375,7 @@ raw_atomic_long_cmpxchg(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_cmpxchg_acquire() elsewhere.
  *
@@ -1396,6 +1398,7 @@ raw_atomic_long_cmpxchg_acquire(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_cmpxchg_release() elsewhere.
  *
@@ -1418,6 +1421,7 @@ raw_atomic_long_cmpxchg_release(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_cmpxchg_relaxed() elsewhere.
  *
@@ -1440,7 +1444,8 @@ raw_atomic_long_cmpxchg_relaxed(atomic_long_t *v, long old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with full ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_try_cmpxchg() elsewhere.
  *
@@ -1463,7 +1468,8 @@ raw_atomic_long_try_cmpxchg(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with acquire ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_try_cmpxchg_acquire() elsewhere.
  *
@@ -1486,7 +1492,8 @@ raw_atomic_long_try_cmpxchg_acquire(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with release ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_try_cmpxchg_release() elsewhere.
  *
@@ -1509,7 +1516,8 @@ raw_atomic_long_try_cmpxchg_release(atomic_long_t *v, long *old, long new)
  * @new: long value to assign
  *
  * If (@v == @old), atomically updates @v to @new with relaxed ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_try_cmpxchg_relaxed() elsewhere.
  *
@@ -1677,6 +1685,7 @@ raw_atomic_long_add_negative_relaxed(long i, atomic_long_t *v)
  * @u: long value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_fetch_add_unless() elsewhere.
  *
@@ -1699,6 +1708,7 @@ raw_atomic_long_fetch_add_unless(atomic_long_t *v, long a, long u)
  * @u: long value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_add_unless() elsewhere.
  *
@@ -1719,6 +1729,7 @@ raw_atomic_long_add_unless(atomic_long_t *v, long a, long u)
  * @v: pointer to atomic_long_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_inc_not_zero() elsewhere.
  *
@@ -1739,6 +1750,7 @@ raw_atomic_long_inc_not_zero(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_inc_unless_negative() elsewhere.
  *
@@ -1759,6 +1771,7 @@ raw_atomic_long_inc_unless_negative(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_dec_unless_positive() elsewhere.
  *
@@ -1779,6 +1792,7 @@ raw_atomic_long_dec_unless_positive(atomic_long_t *v)
  * @v: pointer to atomic_long_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with full ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * Safe to use in noinstr code; prefer atomic_long_dec_if_positive() elsewhere.
  *
@@ -1795,4 +1809,4 @@ raw_atomic_long_dec_if_positive(atomic_long_t *v)
 }
 
 #endif /* _LINUX_ATOMIC_LONG_H */
-// 4ef23f98c73cff96d239896175fd26b10b88899e
+// 1c4a26fc77f345342953770ebe3c4d08e7ce2f9a

include/linux/mutex.h

@@ -32,11 +32,9 @@
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)
 #endif
 
-#ifndef CONFIG_PREEMPT_RT
-
 #ifdef CONFIG_DEBUG_MUTEXES
 
-#define __DEBUG_MUTEX_INITIALIZER(lockname)				\
+# define __DEBUG_MUTEX_INITIALIZER(lockname)				\
 	, .magic = &lockname
 
 extern void mutex_destroy(struct mutex *lock);
@@ -49,6 +47,7 @@ static inline void mutex_destroy(struct mutex *lock) {}
 
 #endif
 
+#ifndef CONFIG_PREEMPT_RT
 /**
  * mutex_init - initialize the mutex
  * @mutex: the mutex to be initialized
@@ -101,9 +100,6 @@ extern bool mutex_is_locked(struct mutex *lock);
 
 extern void __mutex_rt_init(struct mutex *lock, const char *name,
 			    struct lock_class_key *key);
-extern int mutex_trylock(struct mutex *lock);
-
-static inline void mutex_destroy(struct mutex *lock) { }
 
 #define mutex_is_locked(l)	rt_mutex_base_is_locked(&(l)->rtmutex)
 

kernel/locking/percpu-rwsem.c

@@ -223,9 +223,10 @@ static bool readers_active_check(struct percpu_rw_semaphore *sem)
 
 void __sched percpu_down_write(struct percpu_rw_semaphore *sem)
 {
+	bool contended = false;
+
 	might_sleep();
 	rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_);
-	trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_WRITE);
 
 	/* Notify readers to take the slow path. */
 	rcu_sync_enter(&sem->rss);
@@ -234,8 +235,11 @@ void __sched percpu_down_write(struct percpu_rw_semaphore *sem)
 	 * Try set sem->block; this provides writer-writer exclusion.
 	 * Having sem->block set makes new readers block.
 	 */
-	if (!__percpu_down_write_trylock(sem))
+	if (!__percpu_down_write_trylock(sem)) {
+		trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_WRITE);
 		percpu_rwsem_wait(sem, /* .reader = */ false);
+		contended = true;
+	}
 
 	/* smp_mb() implied by __percpu_down_write_trylock() on success -- D matches A */
 
@@ -247,7 +251,8 @@ void __sched percpu_down_write(struct percpu_rw_semaphore *sem)
 
 	/* Wait for all active readers to complete. */
 	rcuwait_wait_event(&sem->writer, readers_active_check(sem), TASK_UNINTERRUPTIBLE);
-	trace_contention_end(sem, 0);
+	if (contended)
+		trace_contention_end(sem, 0);
 }
 EXPORT_SYMBOL_GPL(percpu_down_write);
 

kernel/locking/qspinlock_paravirt.h

@@ -294,8 +294,8 @@ static void pv_wait_node(struct mcs_spinlock *node, struct mcs_spinlock *prev)
 {
 	struct pv_node *pn = (struct pv_node *)node;
 	struct pv_node *pp = (struct pv_node *)prev;
+	bool __maybe_unused wait_early;
 	int loop;
-	bool wait_early;
 
 	for (;;) {
 		for (wait_early = false, loop = SPIN_THRESHOLD; loop; loop--) {

kernel/locking/rtmutex.c

@@ -237,12 +237,13 @@ static __always_inline bool rt_mutex_cmpxchg_release(struct rt_mutex_base *lock,
  */
 static __always_inline void mark_rt_mutex_waiters(struct rt_mutex_base *lock)
 {
-	unsigned long owner, *p = (unsigned long *) &lock->owner;
+	unsigned long *p = (unsigned long *) &lock->owner;
+	unsigned long owner, new;
 
+	owner = READ_ONCE(*p);
 	do {
-		owner = *p;
-	} while (cmpxchg_relaxed(p, owner,
-				 owner | RT_MUTEX_HAS_WAITERS) != owner);
+		new = owner | RT_MUTEX_HAS_WAITERS;
+	} while (!try_cmpxchg_relaxed(p, &owner, new));
 
 	/*
 	 * The cmpxchg loop above is relaxed to avoid back-to-back ACQUIRE

kernel/locking/rwsem.c

@@ -35,7 +35,7 @@
 /*
  * The least significant 2 bits of the owner value has the following
  * meanings when set.
- *  - Bit 0: RWSEM_READER_OWNED - The rwsem is owned by readers
+ *  - Bit 0: RWSEM_READER_OWNED - rwsem may be owned by readers (just a hint)
  *  - Bit 1: RWSEM_NONSPINNABLE - Cannot spin on a reader-owned lock
  *
  * When the rwsem is reader-owned and a spinning writer has timed out,
@@ -1002,8 +1002,8 @@ rwsem_down_read_slowpath(struct rw_semaphore *sem, long count, unsigned int stat
 
 	/*
 	 * To prevent a constant stream of readers from starving a sleeping
-	 * waiter, don't attempt optimistic lock stealing if the lock is
-	 * currently owned by readers.
+	 * writer, don't attempt optimistic lock stealing if the lock is
+	 * very likely owned by readers.
 	 */
 	if ((atomic_long_read(&sem->owner) & RWSEM_READER_OWNED) &&
 	    (rcnt > 1) && !(count & RWSEM_WRITER_LOCKED))

lib/Kconfig.debug

@@ -1303,7 +1303,7 @@ config PROVE_LOCKING
 	select DEBUG_SPINLOCK
 	select DEBUG_MUTEXES if !PREEMPT_RT
 	select DEBUG_RT_MUTEXES if RT_MUTEXES
-	select DEBUG_RWSEMS
+	select DEBUG_RWSEMS if !PREEMPT_RT
 	select DEBUG_WW_MUTEX_SLOWPATH
 	select DEBUG_LOCK_ALLOC
 	select PREEMPT_COUNT if !ARCH_NO_PREEMPT
@@ -1426,7 +1426,7 @@ config DEBUG_WW_MUTEX_SLOWPATH
 
 config DEBUG_RWSEMS
 	bool "RW Semaphore debugging: basic checks"
-	depends on DEBUG_KERNEL
+	depends on DEBUG_KERNEL && !PREEMPT_RT
 	help
 	  This debugging feature allows mismatched rw semaphore locks
 	  and unlocks to be detected and reported.

scripts/atomic/kerneldoc/add_unless

@@ -10,6 +10,7 @@ cat <<EOF
  * @u: ${int} value to compare with
  *
  * If (@v != @u), atomically updates @v to (@v + @a) with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/cmpxchg

@@ -6,6 +6,7 @@ cat <<EOF
  * @new: ${int} value to assign
  *
  * If (@v == @old), atomically updates @v to @new with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/dec_if_positive

@@ -4,6 +4,7 @@ cat <<EOF
  * @v: pointer to ${atomic}_t
  *
  * If (@v > 0), atomically updates @v to (@v - 1) with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/dec_unless_positive

@@ -4,6 +4,7 @@ cat <<EOF
  * @v: pointer to ${atomic}_t
  *
  * If (@v <= 0), atomically updates @v to (@v - 1) with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/inc_not_zero

@@ -4,6 +4,7 @@ cat <<EOF
  * @v: pointer to ${atomic}_t
  *
  * If (@v != 0), atomically updates @v to (@v + 1) with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/inc_unless_negative

@@ -4,6 +4,7 @@ cat <<EOF
  * @v: pointer to ${atomic}_t
  *
  * If (@v >= 0), atomically updates @v to (@v + 1) with ${desc_order} ordering.
+ * Otherwise, @v is not modified and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *

scripts/atomic/kerneldoc/try_cmpxchg

@@ -6,7 +6,8 @@ cat <<EOF
  * @new: ${int} value to assign
  *
  * If (@v == @old), atomically updates @v to @new with ${desc_order} ordering.
- * Otherwise, updates @old to the current value of @v.
+ * Otherwise, @v is not modified, @old is updated to the current value of @v,
+ * and relaxed ordering is provided.
  *
  * ${desc_noinstr}
  *